Wireless signal transmitting antenna, wireless signal receiving antenna, wireless signal transmitting system, wireless signal transmitting method, and wireless signal receiving method

ABSTRACT

When wireless communication is performed, a signal can be formed into a spiral beam (H), the spiral pitch of the signal can be changed, and a plurality of spiral beams (H) with different spiral pitches can be transmitted and received. A wireless signal transmitting antenna (10) includes a signal emitting means (A) having N number of antenna elements (A1, . . . , AN) (where N is an integer satisfying N≥2) equally spaced on a circumference of circle, and a signal distribution means (B) for generating, from an input first signal (S), N number of second signals (G1, . . . , GN) having a phase difference from one another and outputting the N number of second signals (G1, . . . , GN) to the N number of antenna elements (A1, . . . , AN), respectively, so that a spiral beam (H) with the equiphase surface inclined spirally is output from the signal emitting means (A).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2014/005369, filed on Oct. 22, 2014, the contents of all of whichare incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless signal transmitting antenna,a wireless signal receiving antenna, a wireless signal transmittingsystem, a wireless signal transmitting method, and a wireless signalreceiving method that form signals into spiral beams and wirelesslycommunicate them.

BACKGROUND ART

Communications in the range of frequencies currently used for wirelesscommunications are approaching the limit. To solve this problem, thecommunication technology that adds the orbital angular momentum (OAM) towireless signals to form signals into spiral beams and transmits andreceives them is under study. The signals which are formed into spiralbeams have the characteristics that the equiphase surface is twisted ina spiral form. By changing the spiral pitch of the equiphase surface ofspiral beams, it is possible to form infinite orthogonal mode signals.Therefore, by use of spiral beams for wireless communications, it ispossible to perform multiple communications over the same frequency,thereby achieving higher-speed and higher-capacity communications.

The study on communications using signals in spiral beams to which theorbital angular momentum is added is disclosed in Non Patent Literature1 and Non Patent Literature 2, for example. Non Patent Literature 1discloses formation of a spiral beam where the orbital angular momentumis added to a signal by use of an OAM antenna 50 having a reflectingunit 51 where a cut is made in a part of a parabolic antenna as shown inFIG. 16. Non Patent Literature 2 discloses the experiment showing that,as a result of forming a spiral beam using the OAM antenna 50 andtransmitting a signal, this signal can be received at a receiving pointlocated at a long distance.

CITATION LIST Non Patent Literature

-   NPL1: “BR witnesses experiment on Radio Orbital Angular Momentum    (OAM) with potential for drastic improvement in spectrum    efficiency”, ITU, Internet (URL:    http://www.itu.int/en/ITU-R/trends/OAM/Pages/default.aspx)-   NPL2: Fabrizio Tamburini, and five others, New Journal of Physics    2012 Mar. 1 “Encoding many channels on the same frequency through    radio vorticity: first experimental test”, Internet (URL:    http://iopscience.iop.org/1367-2630/14/3/033001)

SUMMARY OF INVENTION Technical Problem

According to the OAM antenna 50 disclosed in Non Patent Literature 1 andNon Patent Literature 2, it is possible to form a spiral beam andtransmit a signal. For actual high-speed and high-capacitycommunications, multiplexing of a plurality of spiral beams withdifferent spiral pitches is required. However, because the OAM antenna50 physically forms a spiral beam by using the reflecting unit 51 wherea cut is made in a part of a parabolic antenna, it is not possible tochange the spiral pitch of the spiral beam. Thus, the OAM antennadisclosed in Non Patent Literature 1 and Non Patent Literature 2 has aproblem that it is not possible to form a plurality of spiral beams withdifferent spiral pitches.

An exemplary object of the present invention is to provide a wirelesssignal transmitting antenna, a wireless signal receiving antenna, awireless signal transmitting system, a wireless signal transmittingmethod, and a wireless signal receiving method that can, for wirelesscommunications, form a signal into a spiral beam and change the spiralpitch of the signal, and further can use a plurality of spiral beamswith different spiral pitches simultaneously for wirelesscommunications.

Solution to Problem

One exemplary aspect of the present invention is a wireless signaltransmitting antenna including a signal emitting means having N numberof antenna elements (where N is an integer satisfying N≥2) equallyspaced on a circumference of circle; and a signal distribution means forgenerating, from an input first signal, N number of second signalshaving a phase difference from one another and outputting the N numberof second signals to the N number of antenna elements, respectively, sothat a spiral beam with an equiphase surface inclined spirally is outputfrom the signal emitting means.

One exemplary aspect of the present invention is a wireless signalreceiving antenna including a signal receiving means having X number ofantenna elements (where X is an integer satisfying X≥2) equally spacedon a circumference of circle; and a signal synthesis means forreceiving, as X number of second signals, spiral beams with equiphasesurfaces inclined spirally received by the signal receiving means fromthe X number of antenna elements, respectively, adding a phasedifference to each of the X number of second signals, and synthesizingand outputting a first signal.

One exemplary aspect of the present invention is a wireless signaltransmitting method including generating, from an input first signal, Nnumber of second signals having a phase difference from one another; andoutputting the N number of second signals to N number of antennaelements, respectively, so that a spiral beam with an equiphase surfaceinclined spirally is output from a signal emitting means having the Nnumber of antenna elements (where N is an integer satisfying N≥2)equally spaced on a circumference of circle.

One exemplary aspect of the present invention is a wireless signalreceiving method including receiving, as X number of second signals, aspiral beam with equiphase surface received by a signal receiving meanshaving X number of antenna elements (where X is an integer satisfyingX≥2) equally spaced on a circumference of circle from the X number ofantenna elements, respectively, adding a phase difference to each of theX number of second signals, synthesizing a first signal therefrom andoutputting the first signal.

One exemplary aspect of the present invention is a wireless signaltransmitting system including a signal emitting means for outputting atransmission signal by N number of antenna elements (where N is aninteger satisfying N≥2); and a signal distribution means for generating,from an input first signal, N number of second signals having a phasedifference from one another, and outputting the N number of secondsignals to the N number of antenna elements, respectively, wherein the Nnumber of antenna elements are equally spaced on a circumference ofcircle.

Advantageous Effects of Invention

According to the wireless signal transmitting antenna, the wirelesssignal receiving antenna, the wireless signal transmitting system, thewireless signal transmitting method and the wireless signal receivingmethod according to the exemplary aspects of the present invention, itis possible to form a signal into a spiral beam and change the spiralpitch of the signal for wireless communications, and further to use aplurality of spiral beams with different spiral pitches simultaneouslyfor wireless communications.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing the structure of a wireless transmittingantenna according to a first exemplary embodiment.

FIG. 2 is a view showing the principle of a signal distribution circuitusing a Butler matrix feeding circuit.

FIG. 3 is a view showing the way a spiral beam is formed by a signalemitting means A.

FIG. 4 is a view showing the principle of a signal distribution circuitusing a Butler matrix feeding circuit with a plurality of input ports.

FIG. 5 is a flowchart showing a process of forming a spiral beam by thewireless transmitting antenna.

FIG. 6 is a view showing the structure of a signal distribution circuitincluded in a wireless transmitting antenna according to a secondexemplary embodiment.

FIG. 7 is a view showing the state where M number of different firstsignals are input to the wireless transmitting antenna.

FIG. 8 is a flowchart showing a process of forming M number of differentspiral beams by the wireless transmitting antenna.

FIG. 9 is a view showing the structure of a wireless receiving antennaaccording to a third exemplary embodiment.

FIG. 10 is a flowchart showing a process of receiving a spiral beam bythe wireless receiving antenna.

FIG. 11 is a view showing the structure of a signal synthesis circuitincluded in a wireless receiving antenna according to a fourth exemplaryembodiment.

FIG. 12 is a flowchart showing a process of receiving M number ofdifferent spiral beams by the wireless receiving antenna.

FIG. 13 is a view showing the structure of a wireless transmitting andreceiving system according to a fifth exemplary embodiment.

FIG. 14 is a view showing a modified example of a wireless transmittingantenna according to a seventh exemplary embodiment.

FIG. 15 is a view showing the structure of a wireless transmittingantenna according to an eighth exemplary embodiment.

FIG. 16 is a view showing an OAM antenna according to related art.

DESCRIPTION OF EMBODIMENTS First Exemplary Embodiment

Exemplary embodiments of the present invention are described hereinafterwith reference to the drawings.

First Exemplary Embodiment

As shown in FIG. 1, a wireless transmitting antenna (wirelesstransmitting system) 10 includes a signal emitting means A having Nnumber of antenna elements A1, A2, . . . , AN (where N is an integer of2 or more) that are equally spaced on the circumference of circle, asignal input port (signal input means) C for inputting first signals S1,. . . , SM, and a signal distribution circuit (signal distributionmeans) B for distributing the input first signals S1, . . . , SM to Nnumber of second signals S2 with equal power and outputs them to theantenna elements A1, A2, . . . , AN, respectively. By this structure,the wireless transmitting antenna 10 can form and transmit, from theinput first signals S1, . . . , SM, a transmission signal in a spiralbeam by the antenna elements A1, A2, . . . , AN.

The antenna elements A1, . . . , AN are equally spaced on thecircumference of circle with a diameter of 30 cm, for example. Thoseplurality of antenna elements A1, . . . , AN constitute the signalemitting means A. The signal emitting means A corresponds to thereflecting unit 51, which is a parabolic antenna with a cut shown inFIG. 16. A parabolic antenna may be used as each of the antenna elementsA1, . . . , AN, for example. The signal emitting means A and the signaldistribution circuit B are connected through a signal waveguide D. Thesignal waveguide D has N number of signal lines D1, . . . , DN withequal length. The signal lines D1, . . . , DN connect N number of signalemitting ports B1, . . . , BN of the signal distribution circuit B andthe antenna elements A1, . . . , AN. Coaxial cables or waveguides may beused as the signal lines D1, . . . , DN.

The signal distribution circuit B distributes the first signal S that isinput from any of the plurality of signal input ports C1, . . . , CM toN number of second signals G1, . . . , GN with equal power and emit themfrom the signal emitting ports B1, . . . , BN. A Butler matrix feedingcircuit, for example, may be used as the signal distribution circuit B.The Butler matrix is generally known to be used for changing thedirection of transmitting beams.

As shown in FIG. 2, according to the signal distribution circuit B usinga Butler matrix feeding circuit, when the first signal S1 is input fromthe signal input port C1, N number of second signals G1, . . . , GN withequal power are output in a distributed manner from the signal emittingports B1, . . . , BN. At this time, the signal distribution circuit Badds a phase difference with a linear slope θ1 to the N number of secondsignals G1, . . . , GN to be emitted from the signal emitting ports B1,. . . , BN. A spiral beam H is formed using such properties. To bespecific, the signal lines D1, . . . , DN with equal length areconnected from the signal emitting ports B1, . . . , BN to the antennaelements A1, . . . , AN (see FIG. 1).

Further, the antenna elements A1, . . . , AN are equally spaced on thecircumference of circle. Thus, when the second signals G1, . . . , GNare emitted from the antenna elements A1, . . . , AN sequentially atspecified intervals in a certain twist direction (rightward twist orleftward twist), the spiral beam H is formed from the signal emittingmeans A as shown in FIG. 3. The direction of twist of the spiral beam ischanged according to the correspondence between the antenna elements A1,. . . , AN and the signal lines D1, . . . , DN. The mode of the OAM toform the spiral beam H involves the case of N=2. In the case of N=2, thetwist direction may be any of rightward twist and leftward twist. In thecase of N=3 or more, the twist direction of the spiral beam H can bedetermined.

As shown in FIG. 4, the Butler matrix generally has a plurality ofsignal input ports C1, . . . , CM (where M is a positive integersatisfying M≤N), and by changing the signal input ports C1, . . . , CMfor inputting the first signals S1, . . . , SM, it is possible to changethe slope ON of a linearly sloped phase difference that appears at thesignal emitting ports B1, . . . , BN. For example, the first signal S2that is input to the signal input port C2 is output as the secondsignals G1, . . . , GN to which a phase difference with a linear slopeθ2 is added. Using such properties, the spiral pitch of the spiral beamH can be changed corresponding to the signal input ports C1, . . . , CM.Thus, it is possible to form a signal to be output from the signalemitting means A as the spiral beam H having the spiral pitchcorresponding to the signal input ports C1, . . . , CM, the equiphasesurface of which is inclined spirally.

Specifically, the signal distribution circuit B generates, from theinput first signal S, the N number of second signals G1, . . . , GNhaving a phase difference from one another, and outputs the N number ofsecond signals G1, . . . , GN to the N number of antenna elements A1, .. . , AN, respectively, so that the spiral beam H, the equiphase surfaceof which is inclined spirally, is output from the signal emitting meansA. At this time, the signal distribution circuit B distributes thesignal so that the second signals G1, . . . , GN having a specifiedphase difference, the phase difference increasing in incremental steps(by equal differences) in the circumferential direction, are input tothe antenna elements A1, . . . , AN that are adjacent in the signalemitting means A. Although an example of using a Butler matrix feedingcircuit for the signal distribution circuit B is shown in the abovedescription, any circuit may be used as long as it can output the secondsignals G1, . . . , GN so that the spiral beam H is formed from each ofthe antenna elements A1, . . . , AN that are equally spaced on thecircumference of circle. Further, the phase differences added to thesecond signals are not necessarily at equal intervals (at equaldifferences).

A process of a wireless transmitting method that forms the spiral beam Hby the wireless transmitting antenna 10 is briefly described hereinafterwith reference to FIG. 5.

In the wireless transmitting antenna 10, the signal distribution circuitB distributes the first signal S that is input to any of the signalinput ports C1, . . . , CM into the N number of second signals G1, . . ., GN with equal power (S100). The signal distribution circuit B adds anincremental phase difference to each of the N number of second signalsG1, . . . , GN to be output (S101). The signal distribution circuit Bdistributes the N number of second signals G1, . . . , GN to the Nnumber of antenna elements A1, . . . , AN, respectively, so that thespiral beam H, the equiphase surface of which is inclined spirally, isformed from the signal emitting means A (S102).

As described above, according to the wireless transmitting antenna 10,the signal that is output from each of the antenna elements A1, . . . ,AN can be formed as the spiral beam H whose equiphase surface isinclined spirally. Further, according to the wireless transmittingantenna 10, when forming the signal into the spiral beam H, the spiralpitch of the spiral beam H can be changed arbitrarily.

Second Exemplary Embodiment

In the first exemplary embodiment, the signal that is output from eachof the antenna elements A1, . . . , AN is formed as the spiral beamhaving the spiral pitch corresponding to the signal input ports C1, . .. , CM, the equiphase surface of which is inclined spirally, in thewireless transmitting antenna 10. In this exemplary embodiment, aplurality of spiral beams having different spiral pitches are formedusing the wireless transmitting antenna 10 for multiplexingcommunications. In the following description, the same names and symbolsare used for the parts that are the same as those in the first exemplaryembodiment, and the redundant description is omitted as appropriate.

As shown in FIG. 6, the wireless transmitting antenna 10 includes asignal distribution circuit B that has a plurality of signal input portsC1, . . . , CM and a plurality of signal emitting ports B1, . . . , BN.The structure of the signal distribution circuit B which has an 8 (=M)input, 8 (=N) output Butler matrix feeding circuit is shown in thisexample. When the first signals S1, . . . , SM are input to any of thesignal input ports C1, . . . , CM, phase differences with differentlinear slopes are added thereto, and N number of second signals G1, . .. , GN with equal power are output from the signal emitting ports B1, .. . , BN, respectively (see FIG. 4). Thus, from the input first signalS, M number of spiral beams H1, . . . , HM with different spiral pitchesare formed corresponding to the signal input ports C1, . . . , CM.

As shown in FIG. 7, when M number of different first signals S1, . . . ,SM are respectively input to the M number of signal input ports C1, . .. , CM, phase differences with different linear slopes θ1, . . . , θNare added respectively to the N number of second signals G1, . . . , GNwith equal power corresponding to the signal input ports C1, . . . , CM,and the N number of second signals G1, . . . , GN with equal power arerespectively output from the signal emitting ports B1, . . . , BN. Thesecond signals G1, . . . , GN corresponding to the signal input portsC1, . . . , CM are sequentially output from the antenna elements A1, . .. , AN at specified times at equal intervals, and M number of spiralbeams H1, . . . , HM with different spiral pitches are thereby formedsimultaneously. Therefore, the wireless transmitting antenna 10 cansimultaneously multiplex and transmit the plurality of spiral beams H1,. . . , HM.

A process of a wireless transmitting method that forms the plurality ofspiral beams H with different spiral pitches by the wirelesstransmitting antenna 10 is briefly described hereinafter with referenceto FIG. 8.

In the wireless transmitting antenna 10, the signal distribution circuitB distributes and outputs each of the M number of different firstsignals S1, . . . , SM that are input to each of the signal input portsC1, . . . , CM into the N number of second signals G1, . . . , GN withequal power corresponding to the signal input ports C1, . . . , CM(S200). The signal distribution circuit B adds a different incrementalphase difference to each of the N number of distributed second signalsG1, . . . , GN and outputs them from the signal emitting ports B1, . . ., BN (S201). The signal distribution circuit B distributes the secondsignals G1, . . . , GN to the N number of antenna elements A1, . . . ,AN, respectively, so that the signal emitting means A forms the M numberof different spiral beams H, the equiphase surfaces of which areinclined spirally (S202).

As described above, according to the wireless transmitting antenna 10,it is possible to simultaneously multiplex and transmit the plurality ofspiral beams H1, . . . , HM.

Third Exemplary Embodiment

An antenna that has the same structure as the wireless transmittingantenna 10 can be used also as a receiving antenna for the wirelesstransmitting antenna 10.

As shown in FIG. 9, a wireless receiving antenna 20 includes a signalreceiving means K having X number of antenna elements K1, . . . , KX(where X is an integer of 2 or more) that are equally spaced on thecircumference of circle, a signal synthesis circuit (signal synthesismeans) T for synthesizing a first signal Q from X number of secondsignals P1, . . . , PX with equal power that are received from theantenna elements K1, . . . , KX, respectively, and a signal output meansR having Y number of signal output ports R1, . . . , RY (where Y is apositive integer satisfying Y≤X) for outputting the first signal Q. Bythis structure, the wireless receiving antenna 20 outputs the receivedspiral beam H as the first signal Q from the signal output ports R1, . .. , RY. The number X of the antenna elements K1, . . . , KX may begreater than the number N of the antenna elements A1, . . . , AN in thewireless transmitting antenna 10.

The antenna elements K1, . . . , KX are equally spaced on thecircumference of circle with a diameter of 30 cm, for example. Thoseplurality of antenna elements K1, . . . , KX constitute the signalreceiving means K. A parabolic antenna may be used as each of theantenna elements K1, . . . , KX, for example. The signal receiving meansK and the signal synthesis circuit T are connected through a signalwaveguide U. The signal waveguide U has X number of signal lines U1, . .. , UX with equal length. The signal lines U1, . . . , UX connect Xnumber of signal input ports V1, . . . , VX of the signal synthesiscircuit T and the antenna elements K1, . . . , KX. Coaxial cables orwaveguides may be used as the signal lines U1, . . . , UX.

The signal synthesis circuit T synthesizes a signal from the secondsignals P1, . . . , PX with equal power that are input from theplurality of signal input ports V1, . . . , VX and outputs thesynthesized signal as the first signal Q from any of the signal outputports R1, . . . , RY in accordance with the spiral pitch of the spiralbeam H. A Butler matrix feeding circuit may be used as the signalsynthesis circuit T, for example. The signal synthesis circuit T has thesame structure as the signal distribution circuit B in the wirelesstransmitting antenna 10 (see FIG. 2). Thus, if the second signals P1, .. . , PX are input to the signal distribution circuit B in an oppositemanner, the first signal Q is synthesized and output, which is theoperation of the signal synthesis circuit T. Therefore, the wirelessreceiving antenna 20 can output the spiral beam H as the first signal Qby the operation opposite to the operation of the wireless transmittingantenna 10.

Specifically, the spiral beam whose equiphase surface is inclinedspirally which is received by the signal receiving means K having the Xnumber of antenna elements K1, . . . , KX equally spaced on thecircumference of circle is input as the X number of second signals P1, .. . , PX to the signal synthesis circuit T from the X number of antennaelements K1, . . . , KX, respectively, and the signal synthesis circuitT adds a phase difference to each of the X number of second signals P1,. . . , PX, synthesizes the first signal Q therefrom, and outputs thefirst signal Q. Then, the signal synthesis circuit T adds a specifiedphase difference to the X number of second signals P1, . . . , PX thatare input from the antenna elements adjacent in the signal receivingmeans K so that the phase difference decreases in decremental steps inthe circumferential direction.

Although an example of using a Butler matrix feeding circuit for thesignal synthesis circuit T is shown in the above description, anycircuit may be used as long as it can receive the spiral beam H fromeach of the antenna elements K1, . . . , KX equally spaced on thecircumference of circle and output the first signal Q. Further, thephase differences to be added to the second signals P1, . . . , PX arenot necessarily at equal intervals.

A process of receiving the spiral beam H by the wireless receivingantenna 20 is described hereinafter with reference to FIG. 10.

When the spiral beam H is transmitted from the wireless transmittingantenna 10, the wireless receiving antenna 20 sequentially receives thesecond signals P1, . . . , PX in a certain twist direction from the Xnumber of antenna elements K1, . . . , KX, respectively, that areequally spaced on the circumference of circle (S300). Because anincremental phase difference has been added to each of the secondsignals P1, . . . , PX, the signal synthesis circuit T adds adecremental phase difference, inversely to the incremental phasedifference, to each of the second signals P1, . . . , PX and synthesizestherefrom (S301). The signal synthesis circuit T outputs the firstsignal Q from any of the signal output ports R1, . . . , RY (S302).

As described above, according to the wireless receiving antenna 20, itis possible to output the received spiral beam H as the first signal Q.

Fourth Exemplary Embodiment

The wireless receiving antenna 20 can receive Y number of multiplexedspiral beams H with different spiral pitches that are transmitted by thewireless transmitting antenna 10 in the second exemplary embodiment andoutput them as Y number of first signals Q. In the followingdescription, the same names and symbols are used for the parts that arethe same as those in the other exemplary embodiments, and the redundantdescription is omitted as appropriate.

As shown in FIG. 11, the wireless receiving antenna 20 includes a signalsynthesis circuit T having a plurality of signal input ports V1, . . . ,VX and a plurality of signal output ports R1, . . . , RY. The structureof the signal synthesis circuit T that has a Butler matrix feedingcircuit where X=8 and Y=8 is shown in this example. The signal synthesiscircuit T has the same structure as the signal distribution circuit B inthe second embodiment. Specifically, when the signal synthesis circuit Treceives Y number of spiral beams with different spiral pitches, it addslinear phase differences having slopes that are inverse of the slopescorresponding to the signal output ports R1, . . . , RY to the X numberof received second signals P1, . . . , PX, respectively, synthesizes theY number of first signals Q therefrom, and outputs the Y number of firstsignals Q from the signal output ports R1, . . . , RY, respectively, bythe opposite operation to the signal distribution circuit B.

A process of receiving signals containing Y number of spiral beams Hwith different spiral pitches by the wireless receiving antenna 20 isdescribed hereinafter with reference to FIG. 12.

When the Y number of spiral beams H with different spiral pitches aretransmitted from the wireless transmitting antenna 10, the wirelessreceiving antenna 20 receives the second signals P1, . . . , PX in acertain twist direction respectively from the X number of antennaelements K1, . . . , KX that are equally spaced on the circumference ofcircle (S400). Because an incremental phase difference has been added tothe second signals P1, . . . , PX, the signal synthesis circuit T adds adecremental phase difference, inversely to the incremental phasedifference, to each of the second signals P1, . . . , PX and synthesizesthe first signals Q therefrom (S401). The signal synthesis circuit Toutputs the Y number of first signals Q from the signal output ports R1,. . . , RY (S402).

As described above, according to the wireless receiving antenna 20, itis possible to receive the Y number of multiplexed spiral beams H withdifferent spiral pitches that are transmitted by the wirelesstransmitting antenna 10 and output them as the Y number of first signalsQ.

Fifth Exemplary Embodiment

By the wireless transmitting antenna 10 and the wireless receivingantenna 20 described above, it is possible to wirelessly transmit andreceive signals using the spiral beams H.

As shown in FIG. 13, a wireless transmitting and receiving system 100includes the wireless transmitting antenna 10 and the wireless receivingantenna 20. According to the wireless transmitting and receiving system100, it is possible to transmit and receive signals containing Y numberof multiplexed spiral beams H with different spiral pitches.

Sixth Exemplary Embodiment

As described in Non Patent Literature 2, the spiral beam H increases inoutside diameter like a torus as the transmitting and receiving distancebecomes longer. On the other hand, the diameter of the circumferencewhere the antenna elements K1, . . . , KX are placed of the wirelessreceiving antenna 20 may be changed based on the transmitting andreceiving distance. For example, the diameter of the circumference ofthe wireless receiving antenna 20 may be enlarged when the transmittingand receiving distance is long. Further, in order to suppress anincrease in the outside diameter of the spiral beam H, the diameter ofthe circumference where the antenna elements A1, . . . , AN are placedof the wireless transmitting antenna 10 may be changed based on thetransmitting and receiving distance. For example, the diameter of thecircumference of the wireless transmitting antenna 10 may be enlargedwhen the transmitting and receiving distance is long.

Seventh Exemplary Embodiment

As shown in FIG. 14, the antenna elements A1, . . . , AN of the wirelesstransmitting antenna 10 may be a sub-array of an array antenna, insteadof a parabolic antenna, which forms a wireless transmitting antenna 40.Likewise, the antenna elements K1, . . . , KX of the wireless receivingantenna 20 may be a sub-array of an array antenna, instead of aparabolic antenna (not shown).

Eighth Exemplary Embodiment

As shown in FIG. 15, a wireless transmitting antenna 30 includes Mnumber of other signal input ports Z1, . . . , ZN for inputting M numberof different other first signals W orthogonal to the first signal S forforming a spiral beam J which is an orthogonally polarized wave of thespiral beam H transmitted by the wireless transmitting antenna 10, andanother signal distribution circuit E that receives other first signalsW and outputs N number of other second signals F1, . . . , FN orthogonalto the second signals G1, . . . , GN. The wireless transmitting antenna30 can thereby transmit a spiral beam I with VH-polarized waves. Withuse of a wireless receiving antenna (not shown) having the samestructure as the wireless transmitting antenna 30, it is possible toreceive the spiral beam I with VH-polarized waves and output M number offirst signals and M number of different other first signals.

It should be noted that the present invention is not limited to theabove-described exemplary embodiment and may be varied in many wayswithin the scope of the present invention. For example, for the antennaelements A1, . . . , AN and the antenna elements K1, . . . , KX, dipoleantennas, helix antenna or horn antennas may be used, for example,besides those described in the above exemplary embodiments. Further, forthe antenna elements K1, . . . , KX at the receiving end, Yagi antennasmay be used.

Although the present invention is described as a hardware configurationin the above exemplary embodiments, the present invention is not limitedthereto. The present invention may be implemented by performing givenprocessing by DSP (Digital Signal Processing), and it can be implementedby executing a program on DSP (Digital Signal Processor) or implementedwith a logic circuit configured on FPGA (Field Programmable Gate Array)or ASIC (Application Specific Integrated Circuit).

The program can be stored and provided to the computer using any type ofnon-transitory computer readable medium. The non-transitory computerreadable medium includes any type of tangible storage medium. Examplesof the non-transitory computer readable medium include magnetic storagemedia (such as floppy disks, magnetic tapes, hard disk drives, etc.),optical magnetic storage media (e.g. magneto-optical disks), CD-ROM(Read Only Memory), CD-R, CD-R/W, and semiconductor memories (such asmask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM(Random Access Memory), etc.). The program may be provided to a computerusing any type of transitory computer readable medium. Examples of thetransitory computer readable medium include electric signals, opticalsignals, and electromagnetic waves. The transitory computer readablemedium can provide the program to a computer via a wired communicationline such as an electric wire or optical fiber or a wirelesscommunication line.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the claims.

REFERENCE SIGNS LIST

-   10 WIRELESS TRANSMITTING ANTENNA-   20 WIRELESS RECEIVING ANTENNA-   30 WIRELESS TRANSMITTING ANTENNA-   40 WIRELESS TRANSMITTING ANTENNA-   50 OAM ANTENNA-   51 REFLECTING UNIT-   100 WIRELESS TRANSMITTING AND RECEIVING SYSTEM-   A SIGNAL EMITTING MEANS-   A1, . . . , AN ANTENNA ELEMENT-   B SIGNAL DISTRIBUTION CIRCUIT-   B1, . . . , BN SIGNAL EMITTING PORT-   C1, . . . , CM SIGNAL INPUT PORT-   D SIGNAL WAVEGUIDE-   D1, . . . , DN SIGNAL LINE-   E SIGNAL DISTRIBUTION CIRCUIT-   F1, . . . , FN OTHER SECOND SIGNAL-   G1, . . . , GN SECOND SIGNAL-   H SPIRAL BEAM-   H1, . . . , HM SPIRAL BEAM-   I SPIRAL BEAM-   J SPIRAL BEAM-   K SIGNAL RECEIVING MEANS-   K1, . . . , KX ANTENNA ELEMENT-   M INTEGER-   N INTEGER-   P1, . . . , PX SECOND SIGNAL-   Q FIRST SIGNAL-   R SIGNAL OUTPUT MEANS-   R1, . . . , RY SIGNAL OUTPUT PORT-   S1, . . . , SM FIRST SIGNAL-   T SIGNAL SYNTHESIS CIRCUIT-   W FIRST SIGNAL-   X INTEGER-   Y INTEGER-   Z1, . . . , ZN SIGNAL INPUT PORT

The invention claimed is:
 1. A wireless signal transmitting antennacomprising: a signal emitter configured to have N number of antennaelements (where N is an integer satisfying N≥2) equally spaced on acircumference of a circle; a first signal distributor configured togenerate, from an input first signal, N number of second signals havinga phase difference from one another, and output the N number of secondsignals to the N number of antenna elements, respectively, so that aspiral beam with an equiphase surface inclined spirally is output fromthe signal emitter; and a second signal distributor configured toreceive a third signal having a phase orthogonal to that of the firstsignal, and output N number of fourth signals having phases orthogonalto those of the second signals so that orthogonally polarized waves ofthe spiral beam are formed by the signal emitter, wherein when M numberof different first signals (where M is an integer satisfying M≤N) and Mnumber of different third signals are input, the first signaldistributor and the second signal distributor generate and output thesecond signals and the fourth signals to each of the N number of antennaelements, respectively, so that M number of different spiral beams areoutput from the signal emitter, and wherein the first signal distributorand the second signal distributor distribute the second signals and thefourth signals, respectively, so that signals having a specified phasedifference, which increases in an incremental manner in acircumferential direction, are input to adjacent antenna elements in thesignal emitter.
 2. The wireless signal transmitting antenna according toclaim 1, wherein a diameter of the circumference where the antennaelements are placed is changed based on a signal transmitting andreceiving distance.
 3. A wireless signal transmitting system comprising:a signal emitter configured to output a transmission signal by N numberof antenna elements (where N is an integer satisfying N≥2) equallyspaced on a circumference of a circle; a first signal distributorconfigured to generate, from an input first signal, N number of secondsignals having a phase difference from one another, and output the Nnumber of second signals to the N number of antenna elements,respectively, so that a spiral beam with an equiphase surface inclinedspirally is output from the signal emitter; and a second signaldistributor configured to receive a third signal having a phaseorthogonal to that of the first signal, and output N number of fourthsignals having phases orthogonal to those of the second signals so thatorthogonally polarized waves of the spiral beam are formed by the signalemitter, wherein when M number of different first signals (where M is aninteger satisfying M≤N) and M number of different third signals areinput, the first signal distributor and the second signal distributorgenerate and output the second signals and the fourth signals to each ofthe N number of antenna elements, respectively, so that M number ofdifferent spiral beams are output from the signal emitter, and whereinthe first signal distributor and the second signal distributordistribute the second signals and the fourth signals, respectively, sothat signals having a specified phase difference, which increases in anincremental manner in a circumferential direction, are input to adjacentantenna elements in the signal emitter.
 4. A wireless signaltransmitting method comprising: generating, from an input first signal,N number of second signals having a phase difference from one another;outputting the N number of second signals to N number of antennaelements, respectively, so that a spiral beam with an equiphase surfaceinclined spirally is output from a signal emitter having the N number ofantenna elements (where N is an integer satisfying N≥2) equally spacedon a circumference of a circle; generating, from an input third signalhaving a phase orthogonal to that of the first signal, N number offourth signals having phases orthogonal to those of the second signalshaving a phase difference from one another; and outputting N number ofthe fourth signals so that orthogonally polarized waves of the spiralbeam are formed by the signal emitter, wherein when M number ofdifferent first signals (where M is an integer satisfying M≤N) and Mnumber of different third signals are input, the second signals and thefourth signals are generated and output to each of the N number ofantenna elements, respectively, so that M number of different spiralbeams are output from the signal emitter, and wherein the second signalsand the fourth signals are distributed, respectively, so that signalshaving a specified phase difference, which increases in an incrementalmanner in a circumferential direction, are input to adjacent antennaelements in the signal emitter.
 5. The wireless signal transmittingmethod according to claim 4, wherein a diameter of the circumferencewhere the antenna elements are placed is changed based on a signaltransmitting and receiving distance.
 6. The wireless signal transmittingsystem according to claim 3, wherein a diameter of the circumferencewhere the antenna elements are placed is changed based on a signaltransmitting and receiving distance.